1. Field of the Invention
The present invention relates to oil and gas well drilling and oil and gas well drilling equipment.
The present invention more particularly relates to a sub assembly for carrying a float valve therewithin which allows easy removal of the float valve from the drill string in the event that the lower portion of the drill string becomes stuck during drilling operation.
2. General Background
In the drilling of oil or gas wells, there are many problems which arise due to formation conditions which might warrant the placement of a float valve into the drill string.
One of these conditions might be, for example, a well coming in and a blowout condition which might develop into a catastrophe.
In these cases where a blowout is feared, or a well "coming in," a float valve can be placed in the drill string which float valve helps eliminate problems of a blowout in certain conditions, acting as an inside "BOP" or inside blow out preventor.
Problems exist in the placement of a float valve in the drill string. This is because if the drill string happens to become stuck, it will be thereafter difficult or impossible to remove the float valve from the drill string. Then, normal operations (such as explosives or wire lines) to remove the drill pipe once stuck cannot be used because of the presence of the float valve blocking the drill pipe bore.
It is to this problem that the present invention is directed.
3. General Discussion of the Present Invention
The present invention provides an assembly for carrying a float valve in a drill string which assembly allows easy removal of the float valve from the drill string should the drill string become stuck.
The present invention provides a hanger sub having a first upper connection means for attaching the hanger sub to the drill string or work string. A lower connection portion of the sub provides inner and outer threads, for example, which allow a float valve canister to be mounted (on the inner threads) as well as an outer protective sub to be mounted (on the outer threads) of the hanger sub.
The valve canister contains therewithin a float valve and the float valve is protectively housed therewithin. During operation a charge can be lowered into the drill string and detonated allowing easy detachment of the float valve from the drill string since it is attached to the sub hanger and is easily removable from the hole therewith.
It is thus an object of the present invention to provide an apparatus which allows easy removal of a float valve from the drill string as in the case of the drill string being at least partially stuck in the hole.
It is another object of the present invention to provide a float valve canister assembly which is easy to construct, easy to use, and easy to maintain.
Another object of the present invention is to provide a hanger sub assembly which can be easily constructed at minimum cost.
Still another object of the present invention is to provide a safety tool for use in the drill string which can be used in even possibly hazardous situations since removal of the tool from the drill string is easily achieved.
Another object of the present invention is to provide a method and apparatus for removing stuck drill pipe which contains a float valve therewithin at least partially blocking the drill string bore.
Still another object of the present invention is to provide a method and apparatus for removing stuck drill pipe with a conventional prima cord and wire line, even when a float valve is being used in the drill string.